/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.solr.analysis;

import org.apache.lucene.analysis.shingle.ShingleFilter;
import org.apache.lucene.analysis.TokenStream;
import org.apache.solr.common.SolrException;
import org.apache.solr.common.SolrException.ErrorCode;

import java.util.Map;

/**
 * Factory for {@link ShingleFilter}.
 * 
 * <pre class="prettyprint" >
 * &lt;fieldType name="text_shingle" class="solr.TextField" positionIncrementGap="100"&gt;
 *   &lt;analyzer&gt;
 *     &lt;tokenizer class="solr.WhitespaceTokenizerFactory"/&gt;
 *     &lt;filter class="solr.ShingleFilterFactory" minShingleSize="2" maxShingleSize="2"
 *             outputUnigrams="true" outputUnigramsIfNoShingles="false" tokenSeparator=" "/&gt;
 *   &lt;/analyzer&gt;
 * &lt;/fieldType&gt;
 * </pre>
 * 
 * @version $Id: ShingleFilterFactory.java 1074011 2011-02-24 01:49:49Z koji $
 */
public class ShingleFilterFactory extends BaseTokenFilterFactory {
	private int minShingleSize;
	private int maxShingleSize;
	private boolean outputUnigrams;
	private boolean outputUnigramsIfNoShingles;
	private String tokenSeparator;

	@Override
	public void init(Map<String, String> args) {
		super.init(args);
		maxShingleSize = getInt("maxShingleSize",
				ShingleFilter.DEFAULT_MAX_SHINGLE_SIZE);
		if (maxShingleSize < 2) {
			throw new SolrException(ErrorCode.SERVER_ERROR,
					"Invalid maxShingleSize (" + maxShingleSize
							+ ") - must be at least 2");
		}
		minShingleSize = getInt("minShingleSize",
				ShingleFilter.DEFAULT_MIN_SHINGLE_SIZE);
		if (minShingleSize < 2) {
			throw new SolrException(ErrorCode.SERVER_ERROR,
					"Invalid minShingleSize (" + minShingleSize
							+ ") - must be at least 2");
		}
		if (minShingleSize > maxShingleSize) {
			throw new SolrException(ErrorCode.SERVER_ERROR,
					"Invalid minShingleSize (" + minShingleSize
							+ ") - must be no greater than maxShingleSize ("
							+ maxShingleSize + ")");
		}
		outputUnigrams = getBoolean("outputUnigrams", true);
		outputUnigramsIfNoShingles = getBoolean("outputUnigramsIfNoShingles",
				false);
		tokenSeparator = args.containsKey("tokenSeparator") ? args
				.get("tokenSeparator") : ShingleFilter.TOKEN_SEPARATOR;
	}

	public ShingleFilter create(TokenStream input) {
		ShingleFilter r = new ShingleFilter(input, minShingleSize,
				maxShingleSize);
		r.setOutputUnigrams(outputUnigrams);
		r.setOutputUnigramsIfNoShingles(outputUnigramsIfNoShingles);
		r.setTokenSeparator(tokenSeparator);
		return r;
	}
}
